Auto-tracking spectrophotometer

ABSTRACT

An auto-tracking spectrophotometer has a moveable look-ahead sensor for scanning at least a portion of a color matrix. The look-ahead sensor finds a portion of the color matrix for measurement by an optical system. The optical system for measuring the color matrix is then guided using the information provided by the look-ahead sensor.

This patent application claims the benefit of patent application Ser. No. ______, filed May 5, 2005, and entitled AUTO-TRACKING SPECTROPHOTOMETER.

BACKGROUND OF THE INVENTION

An auto-tracking spectrophotometer (ATS) measures and analyzes spectral data. Since spectral data provides the most complete and accurate description of color, an ATS is the ideal control system for both process and special color print jobs.

An ATS has a table for holding a color composition, a head for performing a scan of the color matrix, and a station, located at one end of the table. In order to use the ATS, an operator places a color graphic composition have a color target on the ATS platen. A vacuum pump is then energized so as to hold the composition onto the table.

The ATS head then scans the entire color target first to locate the beginning and ending points of the color target. After the beginning and ending of the color target are located, the ATS assumes that the color bar proceeds linearly between the beginning and ending of the color bar. Based upon this assumption, the ATS positions its data acquisition optics over what should be the color target, and then scans the area. After the head returns to the station, the measurement is then transmitted to a computer. Software on the computer displays an overview of the color data. The computer or an operator may then adjust the controls of a press used to more accurately reproduce the graphic composition.

ATS have proven invaluable in modern printing plants. However, they have limitations. Care must be taken by the operator of the ATS to align composition in the ATS. If not, the color target may be slightly curved when placed on the table. Further, if the composition is contained on a folded sheet of paper, additional care must be taken to compensate for the fold in the color target. If the color target is not properly aligned, the color target may not be accurately read.

Additionally, at least two scans are required by the ATS. The multiple scans may cause significant time delays. Finally, even with the multiple scans, the alignment of the color target may not be acceptable, resulting in faulty color information.

Further, the scan information is not transmitted to the computer until the head is returned to the station. This delays the time before the data is analyzed, resulting in delays in completing the print job.

An improved ATS which overcomes these problems is thus highly desirable.

SUMMARY OF THE INVENTION

An improved ATS is provided with a look-ahead visual sensor. The look-ahead sensor retrieves an image and a tracking controller finds the location of a color matrix. The color matrix could be a color target, a color profile target, a color bar code, a color picture, or any other amalgamation of colors. A controller moves the data acquisition optics in response to output from the look-ahead sensor. In this way, the data acquisition optics maintains a proper orientation with respect to the color matrix.

Additionally, a stepper motor for controlling movement of the ATS head in an X-direction is controlled directly by the head. Thus, all components for accurately tracking the color bar are located in the head.

In order to improve the efficiency of the ATS, the vacuum pump is provided with a solenoid controlling the coupling of vacuum holes located in the paper table with the vacuum pump.

During the scan, information from the data acquisition optics is continually transmitted to a remote computer by way of a communication channel between the head and the computer. Thus, the computer can immediately begin analyzing the data.

The communication channel is established by way of a communication interface, which could be an Ethernet connection. The head communicates to the by way of an Ethernet connection.

These and other objects, advantages and features of the invention will be more readily understood and appreciated by reference to the detailed description of the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows several auto-tracking spectrophotometers connected to computers by way of a network.

FIG. 2 shows an auto-tracking spectrophotometer.

FIG. 3 shows the contents of the head of an auto-tracking spectrophotometer.

FIG. 4 shows a block diagram of an auto-tracking spectrophotometer.

FIG. 5 is a flowchart showing the operation of an auto-tracking spectrophotometer.

FIG. 6 is a flowchart indicating shows how the color information is collected from color matrix by an auto-tracking spectrophotometer.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a printing plant with several ATS. Computers 10, 12 are connected by way of network 14 to a plurality of ATS systems 16, 18, 20. ATS systems 16, 18, 20 may communicate with computers 10, 12 by way of a standard protocol such as TCP/IP, or, if necessary, by a proprietary communication protocol.

FIG. 2 shows an ATS 20. ATS 20 consists of table 22, head 24, and station 26. Table 22 includes platen 23 and track 25. Table 22 is sample holding surface. In some applications, table 22 could be a curved surface.

Vacuum pump 28 is attached to station 26 by way of tube 30 and vacuum inlet 33. Table 22 has vacuum holes 32. When a graphic composition is placed on table 22, vacuum pump 28 is energized, thus creating a means to hold the graphic composition to table 22. The graphic composition is generally on a substrate, such as paper.

Station 26 includes communication interface 34 and RS232 interface 36. ATS 20 can be connected to a network by way of network interface 34. Network interface 34 could be a standard RJ-45 connection. ATS 20 could be directly connected to a computer by way of RS232 interface 36 or network interface 34.

After a graphic composition is placed on platen 23, head 24 moves across the color chart and reads the color chart on the graphic composition, and transmits the information to a computer.

FIG. 3 shows the contents of head 24. Head 24 serves as an enclosure for various components. Various circuit boards required to operate head 24 are not shown. Arrow 41 shows the movement of the head 24 in the direction of the scan, which is referred to hereinafter as the X-direction. Head 24 includes a NCIS (non-contact image system) 40, data acquisition optics 42, and Y-step motor 44. Y-step motor 44 is connected to data acquisition optics 42 by way of y-drive mechanism 46. Information regarding the location of the color matrix is acquired by non-contact image system 40 and is used to control Y-step motor 44 in order to accurately position data acquisition optics 42 over the color matrix. NCIS 40 is spaced approximately 2 1/2 inches from the data acquisition optics 42. Y-step motor 44 and Y-drive mechanism 46 form a positioning system.

FIG. 4 shows a block diagram of ATS 20. Station 26 includes x-home sensor 52, vacuum control 54, track store 56, communication interface 58, and x-stepper motor 60. X-home sensor 52 detects the x-position of head 24 whenever head 24 is docked with station 26. Vacuum control 54 is connected to vacuum pump 28. Vacuum control 54 controls vacuum inlet solenoid 62. When vacuum control 54 energizes vacuum inlet solenoid 62, a vacuum is applied to table 22. Track store 56 contains information regarding the track such as the length of the track.

Communication interface 58 provides bidrectional communication between ATS 20 and a computer or computers by way of a network. Communication interface 58 includes an Ethernet connection as well as an RS232 interface. X-stepper motor 60 controls the x-position of head 24.

Station 26 is connection to head 24 by way of interface 63 which could be an RS232 serial interface or an LVDS (Low Voltage Digital Signaling) interface. Head 24 includes tracking board 64, y-stepper motor 66, NCIS module 68, DAS (Digital Acquisition System) board 70 and lamp board 72. Tracking board 64 is connected to NCIS module 68 and DAS board 70. Station 26 could be a system for processing or storage of information from head 24. Alternatively, systems other than head station 26 could provided for the processing and storage of information.

Tracking board 64 receives information from NCIS module 68 to control the x-position of head 24 and the y-position of DAS board 70 and lamp board 72. Tracking board 64 is connected to X-stepper motor 60. Tracking board 64 provides commands to X-stepper motor 60 to move head 24. Tracking board 64 is also connected to NCIS module 68. Tracking board 64 uses the information received from NCIS module 68 to correctly position DAS board 70 and lamp board 72 in the y-direction.

DAS board 70 is connected to tracking board 64. DAS board 70 provides the color information to tracking board 64. Tracking board 64 then relays the information by way of interface 63 to station 26 and ultimately to a network or a computer. Lamp board 72 is a known device for acquiring color information from a target.

DAS board 70 could also be used to determine the thickness of the substrate, such as paper, that the image is placed upon. Additionally, the DAS board 70 or NCIS module 68 could be used to determine the speed and direction of movement of head 24.

Rotator 73 allows rotational movements of lamp board 72, the optics within lamp board 72 or head 28. Thus, rotator 73 allows the movement of the optics within DAS board 70 or DAS board 70 about an axis. For example, if a color target on an image were skewed at an angle, then rotator 73 would rotate DAS board 70 or the optics within DAS board 72 to compensate for that angle. The angle is detected by way of NCIS module 68 and tracking board 64.

Map storage system 80 stores maps of various images indicating the location of color targets on the image. For example, a page containing an image could also contain color targets at a known location with reference to the edges of the page or with respect to other reference markers on the page. Station 26 could therefore use a map of the page in order to position head 24 at or near the color targets.

Alternatively, NCIS module 68 and tracking board 64 would then precisely locate the color targets on the page for reading by DAS board 70. NCIS module 68 and tracking board 64 thus act as an alignment system. DAS board 70 could be used with NCIS module 68 and tracking board 64 to locate the color target.

Acquisition of a map or the location of the color targets could come from several sources. For example, a bar code on the image could identify the page and thereby a map of the color targets on the page. Alternatively, an operator could manually select the appropriate map. Or, a central control system could automatically communicate the map definition to the system.

The map would then be loaded from map storage system 82 into memory 84. Memory 84 is shown located within station 26. However, memory 84 could be at any convenient location. Station 26 would then move head 24 to the location of the color target based upon the map.

During a scan, an interpreter would use map information to control the location or operation of the NCIS module 68 or DAS board 70. The interpreter could then be used to insure that head 24 is properly positioned over the image. The interpreter could be a software module within tracking board 64 or station 26. Alternatively, the interpreter could be a discreet component.

As a further alternative, a bar code placed on the page could supply many data parameters to the interpreter system. For example, the bar code could include information regarding the coordinates of the color target. In that case, a bar code reader would read the bar code. A controller, which could be located in station 26, would move the head to the coordinates of the color target indicated by the bar code.

FIG. 5 is a flowchart showing the operation of ATS 20. A color calibration application starts on a computer connected to ATS 20. Step 100. When ATS 20 receives a signal from the computer that an application has started, ATS 20 energizes vacuum pump 28. Step 102. In this way, a vacuum will be immediately accessible at table 22. After a job is selected on the computer (Step 104), the job information is sent to station 26. Step 106. The job information could include data regarding the size of the color matrix such as height, width of individual color patches within the color matrix, number of colors.

From the job information, station 26 calculates the optimal speed for movement of head 24 in the x-direction. Step 108. The PC then sends a command to station 26 to start the color measurement. Step 110. Station 26 then sends a command to DAS board 70 to begin measurement. Step 112. DAS board 70 then initializes itself by performing such tasks as, spinning the color wheels, energizing the lamp, and energizing the sensors. Step 114. DAS board 70 then begins sending information to the computer. Step 116. When communication between the DAS board 70 and the computer is confirmed, station 26 sends a command to tracking board 64 to begin scanning in the x-direction. Step 118. Tracking board 64 then sends a command to x-stepper motor 60 to move head 24 in the x-direction. Step 120.

Tracking board 64, by way of NCIS module 68, then begins to look for the paper edge. Step 122. When a paper edge is detected by tracking board 64, tracking board 64 sends a message to the computer that a paper edge has been found and also sends to the computer the X/Y-location of the paper edges. Step 124. After the edge is found, tracking board 64 by way of NCIS module 68 begins to search for the color matrix. Step 126. When the color matrix is found (step 128) the tracking board 64 stores the x/Y-location of the start of the color matrix in memory. Step 130.

Tracking board 64 controls x-stepper motor 60 and maintains a counter indicative of the x-position of head 24. DAS board 70 then collects color information from the color matrix. Step 132.

FIG. 6 is a flow chart indicating shows how the color information is collected from color matrix 132. Tracking board 64 sends a command to X-stepper motor 60 to move head 24 in the x-direction. Step 200. Tracking board 64 stores the x-location of the head 24 in memory 65. Tracking board 64 by way of the NCIS module 68 detects the Y-location of the color matrix. Step 202. It stores the Y-location in memory 65. Step 204. Because NCIS module 68 is located approximately 2½ inches in advance of lamp board 72, tracking board 64 uses previously stored data regarding location of the color matrix to control the y-position of lamp board 72 with stepper motor 66.

Tracking board 64 retrieves the y-position of the color matrix for the current x-position of the lamp board 72 from memory 65. Step 206. Tracking board 64 then moves lamp board 72 to the current y-position. Step 208. Color information is then read from the color matrix. Step 210. The color information is then sent to the computer. Step 212.

At the same time NCIS module 68, is searching for the edge of the paper. Step 214. If the edge is detected, then the reading of the color matrix ends. Otherwise, the process repeats.

Returning to FIG. 5, after all color information has been collected, 24 head is returned to its original position. Step 134. When head 24 is docked with station 26, ATS 20 sends a message to the computer that head 24 is docked. Step 136. The solenoid is de-energized. Step 138. The color reading is then completed. Step 140.

Color patches are often aligned sequentially on the paper or substrate. Additionally, a color patch may be a solid color or a gradient of the same color. By comparing color threshold information within the patch, the location of either the DAS board 70 or NCIS module 68 relative to the color patch could be determined.

For example, if color patches of different colors were juxtaposed, the color measurement at the center of each color patch would be significantly different than a measurement near the edge of the color patch. Similarly, if a color patch was a gradient of a color, a color measurement at one edge of the color patch would be significantly different than that at the other edge of the color patch. Thus, by detecting the differences in color measurements, the location of DAS board 70 or NCIS module 68 with reference to a particular patch can be determined.

The above description is of the preferred embodiment. Various alterations and changes can be made without departing from the spirit and broader aspects of the invention as defined in the appended claims, which are to be interpreted in accordance with the principles of patent law including the doctrine of equivalents. Any references to claim elements in the singular, for example, using the articles “a,” “an,” “the,” or “said,” is not to be construed as limiting the element to the singular. 

1. An apparatus for color measurement of an image comprising: a first moveable scanning device for producing a first scan of at least a portion of the image; a second moveable scanning device for color measurement of the image; and a positioning system for positioning the second moveable scanning device based upon the first scan.
 2. The apparatus of claim 1 where the first moveable scanning device is moveable relative to the image.
 3. The apparatus of claim 2 further comprising a communication link between the enclosure and a second system for processing or storage.
 4. The apparatus of claim 3 where the second system for processing or storage is located in the station.
 5. The apparatus of claim 3 where the second system for processing or storage is coupled to the second moveable scanning device.
 6. The apparatus of claim 4 further comprising: a rotating means for rotating the second moveable scanning device about at least a first axis.
 7. The apparatus of claim 6 further comprising: an angle detector system for detecting at least one angle of the image.
 8. The apparatus of claim 7 where the rotating means is actuated in response to the angle detector system.
 9. The apparatus of claim 8 where the angle detector system comprises the first moveable scanning device.
 10. The apparatus of claim 9 where the first moveable scanning device and the second moveable scanning device are located within a head and the head is moveable relative to the image.
 11. The apparatus of claim 10 further comprising a first linear movement means for moving the second scanning device in at least a first direction.
 12. The apparatus of claim 11 further comprising a tracking board coupled to the first moveable scanning device and the first linear movement means.
 13. The apparatus of claim 12 where the tracking board is coupled to the second scanning device.
 14. The apparatus of claim 13 further comprising a second linear movement means for moving the head in at least a second direction, the second direction being generally orthogonal to the first direction.
 15. The apparatus of claim 14 where the tracking board is coupled to the second linear movement means.
 16. The apparatus of claim 15 further comprising a sample holding surface for holding the image.
 17. The apparatus of claim 16 further comprising a holder for maintaining the image on the sample holding surface.
 18. The apparatus of claim 17 where the apparatus includes a station, the station being in a fixed position relative to the head.
 19. The apparatus of claim 18 where the station includes the second linear movement means.
 20. The apparatus of claim 19 where the station includes a vacuum control coupled to the vacuum pump.
 21. The apparatus of claim 20 further comprising a communication link between the head and a second system for processing or storage.
 22. The apparatus of claim 21 further comprising a data network connection.
 23. A head for moveably scanning an image comprising: a first scanning device for producing a first scan of a portion of the image; and a second scanning device for producing a second scan of the image, where the first scanning device is positioned so as to precede the second scanning device when the head is moveably scanning an image.
 24. The head of claim 23 where the second scanning device is moveable relative to the first scanning device.
 25. The head of claim 23 further comprising at least one linear movement means for moving the second scanning device in at least a first direction.
 26. The head of claim 23 further comprising: a rotational means for rotating the second scanning device about at least a first axis.
 27. The head of claim 26 further comprising: a linear movement means for moving the second scanning device in a first linear direction.
 28. A method for moving a first scanning device during a scan of an image comprising: detecting image information during the scan; and moving the first scanning device relative to the image during the scan based upon the image information.
 29. The method of claim 28 where the image has at least a first color threshold and a second color threshold, and further comprises determining a location based upon the first color threshold and the second color threshold.
 30. The method of claim 29 further comprising detecting the image information by moving a second scanning device relative to the image.
 31. The method of claim 29 further comprising: moving the first scanning device and the second scanning device in at least a first direction; and moving the first scanning device relative to the second scanning device in at least a second direction.
 32. The method of claim 31 further comprising: analyzing an output from at least the second device to determine the image information; and moving the first scanning device in at least the second direction to based upon the image information.
 33. The method of claim 32 where the image information indicates an image feature.
 34. The method of claim 33 where a center line is determined from the image feature.
 35. The method of claim 29 where the image is on a color strip further comprising detecting an edge of a color strip.
 36. The method of claim 35 further comprising: an angle of the color strip relative to the first direction.
 37. The method of claim 36 further comprising: compensating for the angle.
 38. The method of claim 37 where the step of compensating for the angle comprises rotating the first scanning device.
 39. The method of claim 34 further comprising: where the image is on a substrate, detecting a substrate edge.
 40. The method of claim 39 further comprising: determining a thickness of the substrate.
 41. The method of claim 40 further comprising: calculating a scan speed.
 42. The method of claim 41 further comprising: obtaining color information about the image from at least the second scanning device.
 43. A method of scanning at least one color patch with a scanner, the scanner having at least first scanning device moveable in at least first direction and a second direction, comprising: determining a location of the at least one color patch; determining at least a first angular orientation of the at least one color patch; and compensating for at least first angular orientation.
 44. The method of claim 43 further comprising rotating the first scanning device.
 45. A system for measuring a color target, the color target contained within an image at a location, comprising: a first memory for storing a map of the image, the map indicating the location of the color target; at least a first scanning device moveable in at least a first direction; and a mechanism for moving the first scanning device to the location.
 46. The system of claim 45 further comprising: an alignment system for aligning the first scanning device with the color target.
 47. The system of claim 46 where the first scanning device and the alignment system are mounted on a head.
 48. The system of claim 47 where the first scanning device is moveable relative to the alignment system.
 49. The system of claim 48 where the alignment system has a wider field of view than the first scanning device.
 50. The system of claim 49 further comprising an interpreter for comparing information from the alignment system with the map.
 51. The system of claim 50 further comprising: a second memory, the second memory containing a plurality of image maps; and a selector for selecting one of the plurality of image maps to be placed into the first memory.
 52. The system of claim 51 where the selector is comprised of a means for interpreting encoded data.
 53. The system of claim 52 where the mechanism is a user assisted device.
 54. A method of measuring a color target, the color target found at a location on an image, comprising: determining the location from a map stored in a memory; moving at least a first scanning device to the location; and scanning the color target.
 55. The method of claim 54 further comprising precisely locating the color target.
 56. The method of claim 55 further comprising: providing at least a first scanning device for precisely locating the color target.
 57. The method of claim 56 further comprising: moving at least a second scanning device to the location.
 58. A method for measuring a color target with at least a first scanning device, the color target found at a location on an image, comprising: determining the location from a map stored in a first memory; moving a second scanning device to the location; precisely determining a position of the color target; and scanning the color target with the first scanning device.
 59. The method of claim 58 further comprising: selecting the map from a plurality of image maps.
 60. The method of claim 59 further comprising: scanning a portion of the image; selecting from the portion a first image map from the plurality of image maps corresponding to the image; and loading the corresponding first image map into the first memory as the map.
 61. The method of claim 60 where the step of scanning a portion of the image comprises: reading encoded data. 